The prior art is replete with numerous examples of friction stir welding devices that are useful in welding various materials. As a general matter, friction stir welding is a technique whereby a rotating tool is brought into forcible contact with an adjacent work piece to be welded, and the rotation of the tool creates frictional heating of the adjacent work piece, and extensive deformation as mixing occurs along a plastic zone. Upon cooling of the plastic zone the work pieces are joined along a welding joint. Examples of prior art friction stir welding devices and other methodologies are more fully disclosed in U.S. Pat. Nos. 4,636,124; 5,460,317; 5,769,306; 5,971,247; 6,079,609; 6,173,880; 6,230,957; 6,237,835; 6,259,052; 6,484,924; 6,613,447; 6,619,534; and 6,729,526, the teachings of which are incorporated by reference herein. It is generally agreed that friction stir welding allows for the autogenous welding of joints with no alloying effects caused by traditional melting operations, such as may be achieved by plasma welding, laser welding, tungsten inert gas welding, etc. As a general matter, friction stir welding typically preserves more of the cast micro-structural properties than other welding methods.
Researchers and designers have faced many challenges with respect to the creation of various new alloys and composite materials that may be used in various industrial and military applications. For example, many new materials are needed where the material needs to possess several different conflicting material properties. For example, extensive research has focused, as of late, on the production of lightweight composite armor, that is, armor that provides protection from large caliber rounds, but is lightweight so that it may be placed or deployed on mobile platforms. In lightweight armor, conflicting material properties present themselves, for example, the new armor must have a desirable microstructure for ballistic resistance and fatigue performance while simultaneously possessing characteristics of ease of forming and joining. The same armor must possess sound ballistic resistance on the outside-facing surface of same, and good structural properties on the inwardly facing surface, which are favorable for structural and ballistic designs.
Therefore, a material-forming tool and a method for forming a material that addresses these and other shortcomings in the prior art practices and techniques utilized heretofore is the subject matter of the present application.